結果:

After repairing the power supply of a big water buffalo PC150NCA, now all the parts found to be broken are replaced, but the power-on output 12V is only 4.2V. The original power supply block is UC3843B, which is not sold locally. I can only buy a UC3843A replacement . I don’t know if the low output voltage has anything to do with this (the optocoupler and the 431 voltage regulator block have also been replaced)